Dynamic braking contactor



April 7, 1 E. F. MEKELBURG 2,881,284 DYNAMIC BRAKING CONTACTOR Filed Sept. 15, 1955 2 Sheets-Sheet 1 y 3 l7 44% g INVENTOR. E KM w zz April 1959 E. F. MEKELBURG v 2,881,284

DYNAMIC BRAKUING CONTACTOR Filed Sept. 15. 1955 2 Sheets-Sheet 2 CowfroZ/rf I INVENTOR. [747/ I i Z Z United States Patent 2,881,284 DYNAMIC BRAKING CONTACTOR Earl F. Mekelburg,

Wauwatosa, Wis., assignor to Square D Company,

This invention relates to a contactor and more particularly to a contactor with a provision for dynamic braking when its controlled device is deenergized for operation in one direction of rotation and immediately reenergized for operation in the opposite direction of rotation.

The object of the invention is a contactor of simple construction which may be adapted to energize a dynamic braking circuit without extensive modification and which may be constructed from conventional and available components.

Another object of the present invention is to provide a contactor having a positively established normal position.

A further object of the present invention is to provide a contactor having a positive positioning means including a mechanical linkage for insuring a desired normal energized position.

A further object of the present invention is a contactor having a pair of movable contacts and positive positioning means including a mechanical linkage between contacts for insuring a desired normal position and further provided with electromagnetic operating means for the movable contacts, one of which being connected for energization in normal position and selected to initially overcome the other and to yield to the other after its energization has been reduced, and the other being selected to overcome the positive positioning means to position both movable contacts one directly and the other through the mechanical linkage.

A further object of the present invention is a contactor having a normal energized position and provided with means for positioning the contactor for energization of an associated circuit and including means for maintaining the contactor in the position of energization of the associated circuit so that only after the associated circuit has performed its function may the contactor be returned to its normal energized position.

A further object of the invention is a contactor for use with a motor controlling device having the provision of means for connecting a dynamic braking circuit to the controlled motor through the contactor upon selection of a reverse direction of rotation for the controlled motor and including means for maintaining the connection of the dynamic braking circuit until the motor speed has been reduced and only then allowing the motor to be energized in the selected reverse direction of rotation.

Further objects and features of the invention will be readily apparent to those skilled in the art from the following specifications and appended drawings illustrating a certain preferred embodiment of the invention in which:

Figure 1 is a front view of the contactor of the present invention.

Figure 2 is a top view of the contactor.

Figure 3 is a sectional view taken along the lines III-III of Figure 1.

Figure 4 is a schematic circuit diagram illustrating the contactor in use with a motor and its controlling device.

The contactor of the present invention consists of a pair of solenoid operated movable contacts having associated 2,881,284 Patented Apr. 7, 1959 stationary contacts and terminals through which the contactor is connected to a device it is to control and is further provided with a mechanical linkage interconnecting the movable contacts whereby the solenoids control not only their associated contacts but, through the mechanical linkage, control the contacts of the other solenoid operated device as well. Spring means are associated with the movable contacts to establish a normal position for the contactor and the solenoids operating the contacts are themselves selected in characteristics to provide a desired characteristic of operation of the contactor as will become more apparent in the specification.

As illustrated in the drawings, the duplicate electromagnetically operated switches are modified with respect to each other only in the selection of a biasing spring and are each provided with facilities to accommodate an interlock to form the contactor of the present invention. The two solenoid operated devices designated A and B are substantially similar in construction and, for that reason, this specification will completely describe only one thereof, it being understood that the other is, except where noted, exactly the same as that device described. The electromagnetic operating mechanism comprises a solenoid 1 having the conventional central core 2 and external bracket 3. A movable magnetizable armature 4 is pivoted at one point on the bracket 3 and is spring biased by a helical coil spring 5 into an open position. The spring 5 operates at one end against a turned out bracket 6 of a spring guide 7 and at its other end against a spring retainer cup 8 retained on a spring guide 9 by a pin 11. The spring guide 9 operates at its forward end by means of a dowel pin 12 therethrough against an armature cover plate 13 secured by screws 14 to the magnetizable armature 4. The spring guide bracket 7 is secured to the bracket 3 of the solenoid 1 by screws 15. Screws 14 also secure to the magnetizable armature 4 a U-shaped contact spring retainer 16 having a central indentation 17 for guiding a helical coil spring 18 operating at one end against the retainer bracket 16 and at the other end against a movable contact carrier 19. The movable contact carrier 19 is biased by the spring 18 against the magnetizable armature 4 and is maintained in alignment by upturned shoulders 21 of the armature face plate 13 so that one end of the movable contact carrier 19 is relatively securely held against the magnetizable armature 4 while the other end extends freely beyond the solenoid coil 1. To the free end of the contact carrier 19 a movable contact 22 is secured by a pair of nuts 23 and is aligned with stationary contact 24 similarly secured to a stationary contact carrying strap 25 secured as by screws 26 to a stationary contact terminal post 27. The relatively rigidly held end of the contact carrier 19 has secured thereto by suitable means as, for instance, the swedging connection shown and described in the copending application of Earl F. Mekelburg, filed February 3, 1953, Serial No. 334,863, issued April 10, 1956, Patent No. 2,741,753, a pair of flexible braided conductors 28. The opposite ends of the braided conductors 28 are similarly secured to a conducting strap 2? attached as by means of screw 31 to a second terminal binding post similar to binding post 27 but not herein shown.

It may be seen that with the solenoid operated contactor, as thus far described, the normal position of deenergization will locate the movable contact carrier 19 and its associated contact 22 spaced from the stationary contact 24 due to the bias of the helical coil spring 5. The limit of this open position of the contactor will be the permissible extent of travel of the spring retainer cup 8 against the lower bracket 32 of the spring retainer plate 7, except as otherwise limited as will be apparent as hereinafter described.

The second solenoid operated contact carrier constitut ing the contactor from the present invention is substantially similar to the solenoid operated contact carrier just described; however, this contact carrier difiers in the bias exerting strength of its helical coil spring 33 constituting the counter part to the helical coil spring of the first described solenoid operated contact carrier. This second solenoid operated contact carrier is provided with a movable contact carrier 35 and a movable contact 36 in cooperating alignment with the stationary contact 37 similar to the contact carrier 19 and stationary and movable contacts 22 and 24, respectively, of the first solenoid operated contact carrier.

Both of the solenoid operated devices constituting the contactor are secured to an insulating base plate 45 by suitable means not herein shown and are parallelly positioned and secured as illustrated. Each device is provided with an extending arm 38 cooperating at their free ends with a pivoted link member 39 in suitable slots 41 and 42 therein. The link member 39 is pivotally supported on a bracket 43 on a shouldered stud 44 passing therethrough with the bracket 43 suitably secured to the insulating base plate 45.

The solenoid coils 1 and 34 of the two devices are provided with suitable terminal posts '46 and 47, respectively, for the energization thereof and terminal screws 48 and 49 are provided for the circuits to be controlled by the contacts 22-24 and 36-37 respectively. The mechanical linkage 39 provided between the two solenoid operated devices in combination with the differences in biasing strength of the helical coil springs 5 and 33 establish a normal position for the contactor, as is shown in Figure 2, with the left-hand contacts 36 and 37 engaged and the right hand contacts 22 and 24 separated. Both helical coil springs 5 and 33 tend to bias their contacts to an open position; however, as has been described, the helical coil spring 5 is much the stronger of the two and through the cooperation of its arm 38 with the pivoted linkage 39 and the arm 38 of the second solenoid operated contact carrier overcomes the spring bias of helical spring 33 to force contacts 36 and 37 into an engaged condition. The limited open position of the contact carriers is now established by the contacts engaged position of the opposite contact carrier.

Referring now to Figure 4 showing schematically one application circuit for the contactor of the present invention, it may be seen that when the contactors are deenergized, contacts 36 and 37 will be engaged and contacts 22 and 24 open due to the previously described stronger bias of helical spring 5 over that of spring 33. In Figure 4, the components of the contactor of the present invention are shown enclosed in dot-dashed lines and associated with these components is shown the energization circuits for running forward and reverse and for dynamic braking of a conventional series motor. These components shown in addition to the parts of the controller are shown merely as illustrative of one application of the present contactor and are not intended to restrict the invention disclosed herein to the particular circuit or devices illustrated. The components shown constitute a motor armature 51 and its series field 52 energized either through forward contacts 53 and 54 or reverse contacts 55 and 56 and an adjustable starting resistor 57 completing the armature circuit of the controlled motor. A dynamic braking circuit is provided shunting the motor armature and series field and constitutes a dynamic braking resistor 58. A controller 59 is provided for selection of the forward and reverse directions of rotation and for energization and deenergization of the contactor through contacts 61 controlled thereby. For the purposes of this circuit and for the use of the present contactor, it should be understood that the controller 59 must pass through an Off condition opening contacts 61 when a reversal of direction of rotation of the motor 51 is desired.

The operation of the contactor with this circuit of Figure 4 when starting from a deenergized condition, as

shown in Figure 4, constitutes the closing of contacts 61 by the controller 59 thereby energizing contactor solenoid A from the source available at lines 62 and 63 to close contacts 22 and 24 and open contacts 36 and 37 through the medium of the mechanical linkage 39. The controller 59, at the time of closing contact 61, selects either a forward or reverse direction of rotation and thereby closes either contacts 53 or 55 and the contacts 54 or 56 associated therewith to establish a direction of current flow through the series field winding 52 to start rotation of the armature 51. Conventional adjustment of the starting resistor 57 will bring the motor up to its running speed in a desired manner.

Should the operator desire a reverse direction of rotation and operation of the controler 59 to a position for establishment of this desired rotation, the new direction of rotation will be selected by operation of the controller 59 which, as has been stated, passes through an oil condition so that the contacts 61 will be opened to deenergize the solenoid 1 to open contacts 22, 24 and close contacts 36, 37 due to the previously described stronger bias of the spring 5 over that of the spring 33. The controller 59 having been placed into the new position for the desired direction of rotation will have closed the selected contacts 53 or 55 and those contacts 54 and 56 associated therewith to establish the reversed energization circuit for the field winding 52 of the motor 51 in series with the dynamic braking resistor 58 now energized through contacts 36 and 37 and in the motor circuit to provide dynamic braking for the motor. It is apparent that the contact 61 will also be closed due to the adjustment of the controller 59; however, the contacts 22 and 24 associated therewith cannot be closed until the force exerted by energized solenoid 1 can overcome the force exerted by solenoid 34 now energized by the dynamic braking current passing therethrough. When the dynamic braking current flowing through solenoid 34 has reduced sulficiently to produce less force than the energized solenoid 1, the contacts 22 and 24 will be closed and contacts 36 and 37 will be opened to open the dynamic braking circuit and close the energization circuit for the armature 51 and series field 52 for direction of rotation opposite to that originally selected. It should be understood that the dynamic braking resistor 58 is shown herein shunting solenoid coil 34 as merely descriptive of a circuit which may be associated with the contactor of the present invention and that the dynamic braking resistor 58 may equally well be in series with the solenoid 34.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given the broadest possible interpretationwithin the terms of the following claims.

What is claimed is:

1. In a device of the character described, the combination comprising; a base, a pair of spaced individual contactor assemblies mounted on the base, each of said assemblies including; an electromagnet assembly, a pivoted armature and a pair of spaced contacts arranged to engage one another whenever the armature is moved from an at rest position to an actuated position in response to the energization of the electromagnet assembly, each of said contactor assemblies also including a spring arranged to normally bias the armatures to the at rest position for maintaining the contacts spaced from each other with the spring of one of the assemblies being of greater strength than the spring of the other assembly, said assemblies being mounted on the base so the armatures thereof are substantially parallel and spaced from each other, a member having a portion secured to the base and a pivot portion spaced equally from the at rest and actuated positions of both armatures, and a beam carried on the pivot portion and in constant engagement with both of the armatures and arranged so the closure of the contacts of one contactor assembly eifects an opening of the contacts on the other contactor assembly and cooperating with the springs for causing the contacts associated with the contactor assembly having the weaker spring to be normally closed whenever the electromagnets of both contactors are tie-energized.

2. A contactor comprising; a base, a first electromagnetically operated switching means mounted on the base and having an open end closed circuit position, a second electromagnetically operated switching means mounted on the base in spaced relation to the first switching means and having an open and closed circuit position, a second spring means associated with each of the switching means arranged to normally move the switching means connected therewith to an open circuit position, and one of said spring means being stronger than the other, means including a lever having a portion secured to the base and beam pivoted on a pivot point spaced equally between the switching means and having a constant interlocking engagement with each of the switch means, said lever being arranged to cooperate with the spring means for moving the switching means associated with the weaker spring to a closed circuit position whenever both of said switch means are de-energized.

3. A contactor comprising; a base, a pair of identical electromagnetically operated switching means mounted in spaced parallel arrangement on the base and having an open and closed circuit position, a spring for each of the switching means arranged for normally holding the switching means in an open circuit position, the spring for one of the switching means being substantially stronger than the spring for the other switching means, and a means including; a member having a portion secured to the base and a pivot portion spaced equally between the switching means and a lever pivoted on the pivot portion and having a constant interlocking engagement with both switching means, said lever being arranged so the closure of one switch efiects an opening of the other end coopcrating with the springs so the contacts of the switch means having the weaker spring will be closed whenever the electromagnets of both switch means are de-energized.

References Cited in the file of this patent UNITED STATES PATENTS 821,009 Whittingham May 22, 1906 1,592,390 Staley July 13, 1926 1,957,381 Barry May 1, 1934 2,064,231 Taylor Dec. 15, 1936 2,446,299 Nelson Aug. 3, 1948 2,755,354 Dehn et a]. July 17, 1956 2, ,2 sw n n G 7 UNETED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,881,284 April 7, 1959 Earl F, Mekelhurg It is herebj certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 9, for "open end read open and line 12, for "a second" read individual column 6 line 12,, for "other end" read other and a Signed and sealed this 11th day of August 1959.

(SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,881,284 April '7, 195

Earl F Mekelhurg It is hereby certified that error appears in the -printed specificatiol of the above numbered patent requiring correction and that the said Letter: Patent should read as corrected below.

Column 5-, line 9, for "open end read open and line 12, for "a second read individual column 6, line 12, for "other end" read other and Signed and sealed this llth day of August 1959,

(SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Ofiicer Commissioner of Patents 

